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Abstract

Colloidal suspensions of multilayer nanoparticles composed of a silver core, a polyelectrolyte spacer layer (inner shell), and a J-aggregate cyanine dye outer shell have been prepared for the first time. Absorption properties of the colloid were measured in the visible region. This multilayer architecture served as a framework for examining the coupling of the localized surface plasmon resonance exhibited by the silver core with the molecular exciton exhibited by the J-aggregate outer shell. The polyelectrolyte spacer layer promotes the formation of an excitonic J-aggregate while serving as a means of controlling the plasmon-exciton (i.e. plexciton) coupling strength through changing the distance between the core and the shell. An analytical expression based on Mie Theory and the Transfer Matrix Method was obtained for describing the optical response of these multilayered nanostructures. Computational and experimental results indicate that the absorption wavelength of the J-aggregate form of the dye is dependent on both the distance of the dye layer from the silver core and the degree of dye aggregation.

Figures (4)

Schematic of (A) a double-shell structure composed of a silver metallic core, a spacer layer consisting of alternating layers PDADMAC/PSS polyelectrolytes, and a 1,1’-diethyl-2,2’-cyanine iodide (PIC) exterior shell. The outer radius and dielectric function of individual layers are (Ri, εi, i = 1,2,…, n). The dielectric function of the medium is εm. (B) The electrostatic adsorption of (PIC) J-aggregates onto a silver core/polyelectrolyte spacer. Na+, Cl-, and I- ions are not drawn for clarity. Figures are not drawn to scale.